383
Colored and Chromophoric Dissolved Organic Matter in Natural Waters
3.1.6 Total Content of Chlorophyll a
Chloropigments (chlorophyll a and carotenoids) could be important determinants of
UV attenuation in natural waters (Zhang et al. 2009; Dupouy et al. 2010; Williamson
et al. 1996; Belzile et al. 2002; Kratzer et al. 2008; Devlin et al. 2009; Lund-Hansen
2004; Morel and Bélanger 2006; Smith et al. 1999; Stambler 2005; Baker and Smith
1982; Gallegos and Bergstrom 2005). Chlorophyll a (Chl a) or phytoplankton biomass shows an absorption maximum around 440 nm (Fig. 4a, c, d) (Zhang et al.
2009; Bowers et al. 2000). Phytoplankton absorption is maximal when Chl a and
phaeophytin-a are detected at the highest levels (Fig. 4a, c, d) (Zhang et al. 2009).
Extraordinary spring blooms of the dinoflagellate Prorocentrum minimum can produce very high concentrations of chlorophyll, which increase for instance light attenuation in the upper Chesapeake Bay (Gallegos and Bergstrom 2005). Chlorophyll a
specific absorption coefficients for both UV and PAR domains are representative of
the dominant picophytoplankton in the Red Sea (Stambler 2005).
The study showed a deep chlorophyll maximum at about 50–60 m, with
~1 × 10 8 cells L −1 dominated by high concentrations of Prochlorococcus
(~75 %), whereas in the Gulf of Eilat (Aqaba) ~4 × 10 7 cells L −1 have been
reported. Eukaryotic algae (~20 %), cyanobacteria (Synechococcus) (~50 %)
and Prochlorococcus (~25 %), are distributed throughout the water column in
the Red Sea (Stambler 2005). Microbial degradation of phytoplankton or chlorophyll a are responsible for the decrease in Chl a or phytoplankton absorption
in waters (Zhang et al. 2009). The share of light attenuation by phytoplankton
is on average 32 % and reaches up to 74 % at high Chl a concentrations in
estuarine-coastal waters (Lund-Hansen 2004). Phytoplankton absorption is the
dominant optical component of light absorption (60–85 %) in spring along the
Patagonia shelf-break front (Ferreira et al. 2009). Therefore the CDOM absorption is significantly dependent on the contents of phytoplankton or total contents of Chl a in natural waters.
3.1.7 Water
Light absorption by natural waters depends on the water quality (clear or turbid, presence of particulate matter, and CDOM content) (Kirk 1984; Hayakawa
and Sugiyama 2008; Gregg and Casey 2009; Fournier 2007; Belzile et al. 2002;
Pérez et al. 2010; Morris 2009; Lund-Hansen 2004; Effler et al. 2010). Recent
studies show that water even in its purest form exhibits a complex absorption
spectrum and a significant amount of scattering caused by refractive index fluctuations (Fournier 2007). The optical properties of natural waters are typically
function of the underwater irradiance and of either the vertical attenuation coefficient for downward irradiance (K d ) or the irradiance reflectance. It is R = E u /E d ,
where E u and E d are the upward and downward irradiance at a given depth (Kirk
1984). These optical properties significantly depend on the nature of the light field
Colored and Chromophoric Dissolved Organic Matter in Natural Waters
3.1.6 Total Content of Chlorophyll a
Chloropigments (chlorophyll a and carotenoids) could be important determinants of
UV attenuation in natural waters (Zhang et al. 2009; Dupouy et al. 2010; Williamson
et al. 1996; Belzile et al. 2002; Kratzer et al. 2008; Devlin et al. 2009; Lund-Hansen
2004; Morel and Bélanger 2006; Smith et al. 1999; Stambler 2005; Baker and Smith
1982; Gallegos and Bergstrom 2005). Chlorophyll a (Chl a) or phytoplankton biomass shows an absorption maximum around 440 nm (Fig. 4a, c, d) (Zhang et al.
2009; Bowers et al. 2000). Phytoplankton absorption is maximal when Chl a and
phaeophytin-a are detected at the highest levels (Fig. 4a, c, d) (Zhang et al. 2009).
Extraordinary spring blooms of the dinoflagellate Prorocentrum minimum can produce very high concentrations of chlorophyll, which increase for instance light attenuation in the upper Chesapeake Bay (Gallegos and Bergstrom 2005). Chlorophyll a
specific absorption coefficients for both UV and PAR domains are representative of
the dominant picophytoplankton in the Red Sea (Stambler 2005).
The study showed a deep chlorophyll maximum at about 50–60 m, with
~1 × 10 8 cells L −1 dominated by high concentrations of Prochlorococcus
(~75 %), whereas in the Gulf of Eilat (Aqaba) ~4 × 10 7 cells L −1 have been
reported. Eukaryotic algae (~20 %), cyanobacteria (Synechococcus) (~50 %)
and Prochlorococcus (~25 %), are distributed throughout the water column in
the Red Sea (Stambler 2005). Microbial degradation of phytoplankton or chlorophyll a are responsible for the decrease in Chl a or phytoplankton absorption
in waters (Zhang et al. 2009). The share of light attenuation by phytoplankton
is on average 32 % and reaches up to 74 % at high Chl a concentrations in
estuarine-coastal waters (Lund-Hansen 2004). Phytoplankton absorption is the
dominant optical component of light absorption (60–85 %) in spring along the
Patagonia shelf-break front (Ferreira et al. 2009). Therefore the CDOM absorption is significantly dependent on the contents of phytoplankton or total contents of Chl a in natural waters.
3.1.7 Water
Light absorption by natural waters depends on the water quality (clear or turbid, presence of particulate matter, and CDOM content) (Kirk 1984; Hayakawa
and Sugiyama 2008; Gregg and Casey 2009; Fournier 2007; Belzile et al. 2002;
Pérez et al. 2010; Morris 2009; Lund-Hansen 2004; Effler et al. 2010). Recent
studies show that water even in its purest form exhibits a complex absorption
spectrum and a significant amount of scattering caused by refractive index fluctuations (Fournier 2007). The optical properties of natural waters are typically
function of the underwater irradiance and of either the vertical attenuation coefficient for downward irradiance (K d ) or the irradiance reflectance. It is R = E u /E d ,
where E u and E d are the upward and downward irradiance at a given depth (Kirk
1984). These optical properties significantly depend on the nature of the light field